You guys really crack me up sometimes... I haven't used my leather gi jacket since I packed up my denim hakama and now you want me to get a helment too???

Peter, traditional Ushiro ate will work just fine. The reason I use the forehead is initially to redirect the person's balance backward and also to stabilise the head to press the point exactly the way I want to. I think the head allows for a bit more control in an actual application scenario as well.

To jk: If you look at the link that Peter gave, think of the same technique shown, but at the point where the shoulders are taken, the forehead is pulled backward instead. The palm is placed on the forehead. The other hand holds the head from behind, pressing the point with thumb or index finger. I actuallly figured this out watching Aikikai guys train (believe it or not) doing some Iriminage / kokyunage variations.

Oh also, this just in:
I was checking out one of my Taiji Chin na manuals and that point at the back of the head is referred to as Naohu and falls on the Governor Vessel meridian (GV-17 acupressure point) and not the Bladder meridian as I said earlier (though the way we hit it, both meridians are affected due to their proximity on that part of the head). The Chin na recommendation says that striking/pressing this point causes fainting as well as shock to the brain (surprise surprise).